A liquid crystal display device is constituted such that a pair of transparent substrates are arranged to face each other in an opposed manner with a liquid crystal layer being sandwiched therebetween. The liquid crystal display device further includes a plurality of gate lines which extend in a first direction (usually horizontal scanning direction) and are arranged parallel to each other, and a plurality of data lines which extend in a second direction (usually vertical scanning direction) and are arranged parallel to each other, such that the plurality of data lines crosses the plurality of gate lines and define pixel regions therebetween. The liquid crystal display device further includes pixel electrodes and common electrodes which are formed in each pixel region on one of the sides of the liquid crystal layer with respect to the said transparent substrates. In such liquid crystal display device, the pixel electrodes are driven by a large number of switching elements, generally thin film transistors, formed on one of the pair of transparent substrates. The switching elements are disposed in the vicinity of the pixel electrodes at respective crossing portions of the gate lines and the data lines. The pixel electrodes and the common electrodes generate an electric field therebetween. The light passes through the region between the pixel electrode and the common electrode, and the quantity of light is controlled by driving the liquid crystals in the liquid crystal layer based on the applied electric field.
Modern liquid crystal display devices implement IPS (in-plane switching) screen technology using a so-called multi-domain structure which provides regions where the twisting directions of liquid crystal molecules become reverse to each other in each pixel. This helps to offset the difference of coloring which is generated when the display is viewed from the left and the right directions. FIG. 6 illustrates a diagrammatic plan view of a liquid crystal display device of IPS type with said multi-domain structure. As shown, adjacent gate lines GL and adjacent data lines DL intersect with each other, and switching elements TFT are provided at the intersections. In a pixel region PXL, defined by the intersection of the adjacent gate lines GL and the adjacent data lines DL, slits SLT are formed which are extending in Y1-Y2 direction. Here, in each pixel region PXL, the slits SLT have comb-shape or the like, with the slits SLT on the Y1-side and the slits SLT on the Y2-side having different inclined angles with respect to the Y1-Y2 direction. With this structure, as indicated by arrows R1 and R2, it is possible to rotate liquid crystal molecules on the Y1-side of the pixel region PXL and liquid crystal molecules on the Y2-side of the pixel region PXL in different rotational directions. In this manner, it is possible to improve viewing angle characteristics of the liquid crystal display device.
With respect to the liquid crystal display device having the above-mentioned constitution, although the multi-domain structure allows an improvement in viewing angle characteristics of the liquid crystal display device, it is known that disturbance of an electric field occurs at a boundary region BA at which the inclined angle of the slits SLT changes within the same pixel region PXL. Herein, a so-called disclination region is generated at the boundary region BA which defines a non-transmitting portion of the pixel region PXL. Thus, such liquid crystal display devices of IPS mode need improvements from the viewpoint of the display quality. The present invention has been made in view of such considerations, and it is an object of the present invention to improve the display quality of such liquid crystal display device.